Her transgender transition was the centrepiece of a much anticipated two-hour programme on the American network ABC.

She told Diane Sawyer that "to all intents and purposes I am a woman" and said she had felt that way since childhood.

"I've always been confused about my gender identity.

"I'm not stuck in anybody's body. My brain is much more female than male. People look at me differently. They see you as this macho male, but my heart and my soul and everything that I do in life it is part of me, that female side is part of me."

In 1976 Jenner earned the reputation as the one of the world's greatest athletes by winning the gold medal in the Olympic decathlon. She went to commercial success in advertising and television. She's been married three times and has six children.

But for the past decade she's been better known as the stepfather in the hit reality TV series Keeping Up With The Kardashians.

"The entire run, I kept thinking to myself, 'Oh my god, this whole thing, the one real true story in the family, was the one I was hiding and nobody knew about it.' The one thing that could really make a difference in people's lives was right here in my soul, and I could not tell that story."

Jenner said she self-identifies as "her" but feels comfortable using the pronouns "he" and "him".

She told Sawyer that Kim Kardashian had handled the news of his transition best, while Khloe had struggled to come to terms with it.

The sisters tweeted that they had watched the interview.

Kim Kardashian wrote: "Love is the courage to live the truest, best version of yourself. Bruce is love. I love you Bruce. #ProudDaughter."

She later added: "Your honesty has opened the doors for others to be courageous and live an authentic life!"

Khloe Kardashian tweeted: "Just finished watching the #BruceJennerInterview with the family. Bruzer, I'm soooo proud of you! Dads really are heros."

The programme was partly celebrity confessional, but a big part was also about educating dumbfounded Americans about transgender issues.

The response is reminiscent of the stunned reaction in Britain last year when boxing promoter Frank Maloney re-emerged as Kelly Maloney - but shock gave way to support.

And on Twitter, there was an explosion of overwhelmingly positive comments. "Courageous", "brave" and "pride" were among the most common words.

The programme marked a farewell to the Bruce that America has grown up with, but she hasn't committed yet to surgery, or a new name.